LTA, a human lung tumor-associated antigen which is found in 86% of lung tumors of all major histologic types, but not in non-lung tumors, normal adult or fetal lung, and other normal tissues, has been further evaluated in terms of its usefulness as a lung cancer marker. We have previously demonstrated increased circulating levels in lung cancer patients using an improved radioimmunoassay and have now extended these results with a solid phase enzyme-linked immunosorbent assay (ELISA). Serum LTA levels were determined in three terminal lung cancer patients and compared to CEA levels for monitoring capability. In all these patients, LTA levels rose dramatically 2-4 months prior to death while CEA levels, at least in two patients, were not predictive of disease recurrence. A major finding was the presence of LTA in bronchial washings from lung cancer patients in concentrations up to 40 times higher than in normal samples. LTA has been further compared to known proteins in the circulation and is not related to any of the 53 serum proteins examined. These studies made use of a second generation antiserum which was raised in a goat against a highly purified LTA preparation. Large quantities of this antiserum were collected and will replace the existing rabbit anti-LTA which has been used in this project since its inception.